Molecules and Ions
Forming Compounds
chemical compounds have constant composition.
formed when elements are chemically combined together in a chemical reaction.
Covalent compounds
Certain covalent compounds with special names
e.g. water, ammonia, methane
prefix is added to distinguish atoms
Penta- (5)
Tetra- (4)
Tri- (3)
Di- (2)
Mono- (1)
second element ends with "-ide"
e.g. hydrogen chloride
Ionic compounds
Polyatomic ions
e.g. nitrate, carbonate
Combining cation and anion
e.g. sodium chloride, where the overall charge is zero.
Negative ions(anions)
e.g. chloride ion
Positive ions(cation)
e.g. sodium ion
Ions
Ionic bonding
transfering of electrons from metal to non-metal atom
Molecules
covalent bonding
occurs between atoms of non-metals
Basic Constituent of matter
Periodic Table
Atomic mass
Symbol of element
Atomic number
Atomic Mass
Weighed average of masses of an element
Isotopes
Difference in number of neutrons
cannot be broken down e.g. carbon
in their simplest form
Atoms
Mass no. = no.of protons + no.of neutrons
No. of protons = No. of electrons
remain the chemical properties of element
smallest particle
Structure of atom
electrons
Relative charge is -1. (-1.6 x 10^-19 C)
Relative mass is 1/1830. (9.11 x 10^-31 Kg)
neutrons
Relative mass is 0. (0C)
Relative mass is 1. (1.67 x 10^-27 Kg)
protons
Relative charge is +1. (+1.6 x 10^-19 C)
Relative mass is 1.(1.67 x 10^-27 Kg)
Classification of matter
Particles
Can be separated by physical methods
distilling
sedimentation
filtering
evaporating
dissolving
Mixtures
Heterogeneous
e.g. salad,concrete
Homogeneous
e.g solutions,milk
Pure Substances
Compounds
atoms of different kinds e.g. water
Elements
atoms of the same kind e.g. oxygen